While the numbers look bleak, some researchers take an optimistic view. "One has to be cautious about simply projecting the patterns of the recent past into the future," says Alba, who believes intermarriage between Hispanics and whites will narrow the gap between the two (see "How important is the melting pot?"). Alba also expects US universities to take steps to enrol more Hispanic students.

But that depends on elementary and high schools preparing Hispanic students for college in the first place. With those schools funded largely through local taxation, the issue becomes whether those who hold disproportionately more of the wealth, namely older whites, are willing to pay for the education of children from another ethnic group.

No one likes to pay taxes without seeing the benefit, so ageing whites may need to be convinced that investing in the education of young Hispanics is vital for their own future. There's a direct connection, argues Dowell Myers, a demographer at the University of Southern California in Los Angeles, as retirees not only need a vibrant and wealthy workforce to pay their retirement benefits, but also to buy their homes if it becomes time to sell.

So there's a deal that older white Americans could strike with young Hispanics: we'll pay for your education if you pay for our retirement. Myers believes this may need to be phrased simply in terms of old and young, so that the charged politics of race don't get in the way.

One encouraging sign is that the Democrat and Republican conventions both featured a prominent speech from a Hispanic politician. This suggests that the political elite is waking up to the fact that more of tomorrow's voters will be of Latin American extraction. The big question: will those voters get to share the American dream?

How important is the melting pot?

Intermarriage with the white majority, it is often said, is the final stage of assimilation into US society for a minority ethnic group.

Hispanics have a higher rate of such intermarriage than similarly disadvantaged African Americans. And some of the children of these marriages merge into the white population. Stephen Trejo at the University of Texas at Austin has found that only about two-thirds of 16- and 17-year-olds with one Mexican parent identify themselves as Mexican, according to the US Census question on Hispanic origin (Journal of Labor Economics, doi.org/dkrbpq).

Since the 1990s, however, the trend of increasing intermarriage between US Hispanics and whites has reversed. According to Daniel Lichter of Cornell University in Ithaca, New York, that seems to have been driven by second-generation US Hispanics reconnecting to their culture by marrying new immigrants (Sociological Forum, doi.org/b5dbv9). If so, reduced migration from Mexico could drive the rate of intermarriage up once more.

Still, Trejo suggests that the US should not rely on the melting pot of intermarriage to narrow the gaps in opportunity afflicting Hispanics. "It'll temper the problem a bit, but it's not going to solve it," he warns.

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Time to strike a deal (Image: William James Warren/Science Faction/Getty)